Who knows about 5.5 hp governor Honda power??

The governor limits the maximum engine speed, full throttle will never be full throttle unless under load or if the engine is off. From the factory the governor is usually calibrated to control engine speed to about 3,600 RPM when the throttle lever is at the full speed position. When the throttle lever is the low speed position the engine should be at a idle possibly around 1,000 - 1,200 RPM. Attached to the throttle lever is a spring that goes to the governor linkage/arm, then from there a linkage rod goes to the carburetor. While the engine is running and the throttle lever is moved to the full speed position it pulls on the governor linkage arm with the pull spring which then opens the carb, soon after as the engine speed goes high enough the governor pulls the link going the carb back to regulate the speed.

Now to your machine. It looks like you have an pneumatic solid solenoid that operates the throttle lever. I would assume that controls the throttle lever to raise or lower the engine speed. It's probably by design, but if you to make the engine idle just disconnect the the solenoid and control the throttle lever manually.